I have often enjoyed city building games like Emperor: Rise of the Middle Kingdom and Children of the Nile. Many online games appear superficially to resemble this style of game--but I have been burned several times when trying them out, discovering that they are actually shallow money-sinks rather than interesting or challenging management games.

I'm wondering whether any good ones actually exist--ftp would be even better of course...

Immortal Cities: Nile Online is shallow imitation of Children of the Nile. It doesn't have nearly the depth of the original game, but it is actually free to play. While it does become a nasty time sink, the good news is that there is an end point; it doesn't just go on forever like an MMO.